ACME modules refactor (#187)

* Move acme.py to acme/__init__.py to prepare splitup.

* Began moving generic code out.

* Creating backends.

* Update unit tests.

* Move remaining new code out.

* Use new interface.

* Rewrite module init code.

* Add changelog.

* Add BackendException for crypto backend errors.

* Improve / uniformize ACME error reporting.

* Create ACMELegacyAccount for backwards compatibility.

* Split up ACMEAccount into ACMEClient and ACMEAccount.

* Move get_keyauthorization into module_utils.acme.challenges.

* Improve error handling.

* Move challenge and authorization handling code into module_utils.

* Add split_identifier helper.

* Move order code into module_utils.

* Move ACME v2 certificate handling code to module_utils.

* Fix/move ACME v1 certificate retrieval to module_utils as well.

* Refactor alternate chain handling code by splitting it up into simpler functions.

* Make chain matcher creation part of backend.

plugins/module_utils/acme/utils.py

@@ -0,0 +1,71 @@
+# -*- coding: utf-8 -*-
+
+# Copyright: (c) 2016 Michael Gruener <michael.gruener@chaosmoon.net>
+# Copyright: (c) 2021 Felix Fontein <felix@fontein.de>
+# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
+
+from __future__ import absolute_import, division, print_function
+__metaclass__ = type
+
+
+import base64
+import re
+import textwrap
+import traceback
+
+from ansible.module_utils._text import to_native
+from ansible.module_utils.six.moves.urllib.parse import unquote
+
+from ansible_collections.community.crypto.plugins.module_utils.acme.errors import ModuleFailException
+
+
+def nopad_b64(data):
+    return base64.urlsafe_b64encode(data).decode('utf8').replace("=", "")
+
+
+def der_to_pem(der_cert):
+    '''
+    Convert the DER format certificate in der_cert to a PEM format certificate and return it.
+    '''
+    return """-----BEGIN CERTIFICATE-----\n{0}\n-----END CERTIFICATE-----\n""".format(
+        "\n".join(textwrap.wrap(base64.b64encode(der_cert).decode('utf8'), 64)))
+
+
+def pem_to_der(pem_filename=None, pem_content=None):
+    '''
+    Load PEM file, or use PEM file's content, and convert to DER.
+
+    If PEM contains multiple entities, the first entity will be used.
+    '''
+    certificate_lines = []
+    if pem_content is not None:
+        lines = pem_content.splitlines()
+    elif pem_filename is not None:
+        try:
+            with open(pem_filename, "rt") as f:
+                lines = list(f)
+        except Exception as err:
+            raise ModuleFailException("cannot load PEM file {0}: {1}".format(pem_filename, to_native(err)), exception=traceback.format_exc())
+    else:
+        raise ModuleFailException('One of pem_filename and pem_content must be provided')
+    header_line_count = 0
+    for line in lines:
+        if line.startswith('-----'):
+            header_line_count += 1
+            if header_line_count == 2:
+                # If certificate file contains other certs appended
+                # (like intermediate certificates), ignore these.
+                break
+            continue
+        certificate_lines.append(line.strip())
+    return base64.b64decode(''.join(certificate_lines))
+
+
+def process_links(info, callback):
+    '''
+    Process link header, calls callback for every link header with the URL and relation as options.
+    '''
+    if 'link' in info:
+        link = info['link']
+        for url, relation in re.findall(r'<([^>]+)>;\s*rel="(\w+)"', link):
+            callback(unquote(url), relation)